


Serving the Mad King

by WhatTheDog



Category: Fate/Grand Order, Fate/stay night & Related Fandoms
Genre: A shitload of kissing, Blow Jobs, M/M, Neck Kissing, Pining, Plot What Plot/Porn Without Plot, listen i just wanted to write these two fucking ok
Language: English
Status: Completed
Published: 2019-06-16
Updated: 2019-06-16
Packaged: 2020-05-12 16:31:04
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,779
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19232866
Author URL: https://archiveofourown.org/users/WhatTheDog/pseuds/WhatTheDog
Summary: With his E-rank luck, Diarmuid never entertained the possibility he'd catch Cú Alter's eye. But somehow he did, and he wouldn't trade the world for anything else.





	Serving the Mad King

**Author's Note:**

> Well, I'm back to hit everybody up with another dose of crackship nonsense. Since I'm in rarepair hell, apparently I have to make the content myself, so here we go. This is just random smut. If you're looking for complexity or deep characterization, this ain't it, chief. I just want these two to bone.
> 
> EDIT: Got bored and beefed this up a little bit. Enjoy!

He still can’t believe his luck.

It was always one of his worst stats. Every time he’d been summoned, his experience was miserable, but mercifully, short. Master after Master had found him lacking, underwhelming, _worthless._

But Cú doesn’t.

From sitting together to lunch to sparring sessions to furtive kissing in shadowed doorways, it still boggles Diarmuid’s mind that Cú chose him. That Cú wants him despite his failures as a knight. There's little good to be said about his fate.

Even so, he almost forgets this when Cú licks and nips his neck.

They’ve just tumbled into his room, and even though both his hands and mind are occupied, Diarmuid has just enough forethought to kick the door closed. He pushes Cú’s hood down, running his fingers through the blue hair, tangling them in the unruly locks. Cú growls in pleasure and stops to kiss Diarmuid’s mouth.

When a soft sigh escapes his lips, Cú chuckles. “You’re eager today.”

Diarmuid stands on his toes, wrapping his arms around the thick neck. “For you, my Lord, _always._ ”

He tries to lace the word with as much desire as possible. Tries to convey how much this means to him, these sessions, these encounters. He had practically melted the first time the Alter smiled at him. Becoming lovers had been beyond his wildest dreams.

But it _happened._ Against all odds, it actually happened.

The next round of kisses begin, and Diarmuid does his best to keep up with his partner’s talented tongue. He savors the way their lips move and their breaths mingle. Together. Breathe in, breathe out. This is almost more intimate for him than sex. He’d do anything to connect with his Lord.

Which is why he doesn’t protest when Cú’s tail wraps around his waist. It pins him against the wall, constricting just enough that he can’t slip out, yet not tight enough to bruise.

He wriggles for show, then puts on a fake pout. “Will I ever be allowed to undress myself?”

“No.” Cú captures his mouth yet again, crushing him against his much larger body. “What good is a present that unwraps itself?”

Stifling a laugh, Diarmuid places his hand against Cú’s chest. He lazily traces the swirls of the tattoos, fingers brushing on top of the nipple just enough to tantalize, but nothing more.

Cú grunts. He grips Diarmuid’s hair, forcing his head back. “Careful with how much you tease. You know I’m not patient.”

Of course Diarmuid knows. That’s why he does it.

He grins. “But, my Lord, haven’t you heard? Good things take time.”

Cú doesn’t even grace him with a reply. He just lightly smacks the top of his head, then nibbles on his jawline, peppering kisses down his throat and sucking his Adam’s apple in such a way that Diarmuid can’t help but moan.

He’s blushing now, both from the noise and the sensation, and Cú regards him with half-lidded eyes.

“You’re redder than your spear.”

Diarmuid leans forward, an action to which Cú reciprocates, letting their lips connect. When they separate, he whispers, “It’s because I was thinking about _your_ spear.”

Unlike earlier, he doesn’t stifle his laugh as Cú groans.

He shakes his head. “You’ve left me no choice. Now I'm  _required_ to punish you.”

Bowing as much as he’s able, what with the wall to his back and the tail around his middle, Diarmuid holds his hand over his heart. “If that is the case, then I willingly accept the price I must pay for my transgressions.” He cups Cú’s face. “You were too lenient on me in America after all.”

Cú suddenly stiffens. He looks away, lips pursed, and Diarmuid’s heart jumps into his throat.

“My Lord, please, I did not mean to upset you—”

“America is irrelevant.” Cú turns back to face him, red eyes glinting in the low light. “We serve a new Master now. Any past performances are null and void.” He nips Diarmuid’s lower lip. “If that doesn’t satisfy you, then I order you to focus on the present.” He grins wolfishly. “Though with how hard I’m going to fuck you, I don’t think you’ll be able to focus on much else.”

“Yes, my Lord,” Diarmuid says, ever obedient as Cú resumes his trajectory past his collarbone. He’s not as forgiving of his mistakes, but he’ll pretend. Anything to make Cú happy.

He leans into the touch as the clawed hands work their way under his clothes. Piece by piece, Cú removes his armor, the caresses growing rougher as more skin is exposed.

Diarmuid bites his fist. His breathing has grown steadily more rapid, and it’s becoming harder and harder to keep from moaning. They haven’t even gotten to the good stuff, yet his cock is already stiff.

When Cú finds his way to his shaft—stroking in a languid, delicious rhythm—Diarmuid breaks his silence. Chest heaving, he _groans_. Fuck, this feels good.

“So loud,” Cú tuts. He taps Diarmuid’s nose. “Let’s keep that mouth occupied, shall we? A good knight should be on his knees.”

He backs up just enough to remove his own clothes, then pushes Diarmuid into a kneeling position. Staring down, he places his hands on his hips and quirks an eyebrow. “You know what to do. What did I say about my patience?”

Diarmuid doesn’t even respond with a “ _yes, my lord_ ” before he takes Cú’s cock into his mouth. He bobs his head up and down on the shaft, swirling his tongue around the glans. A groan lets him know his efforts are appreciated, and he smiles even with Cú’s length in his mouth. Carefully, he slides the cock deeper in, relaxing his gag reflex. Gripping around the base of the shaft, he moves his hands back and forth. Nice, steady motions. Fingers clutch at his hair, and he pulls away to kiss the tip of the cock before leaving a trail up the length, eventually progressing to the inside of Cú's thighs. 

It catches him by surprise when Cú yanks his head back and flings him onto the bed. Pouncing on top of him, Cú spreads his legs, then gives him a sultry look from between them.

“My turn,” he purrs. He takes Diarmuid into his mouth, and _oh God don’t stop, please, my Lord._

Diarmuid grips the sheets tight enough to turn his knuckles white. He pants, his core clenched, his cock throbbing from the heat and wetness of Cú’s mouth. The Alter is relentless, almost brutal, but the knife edge of pleasure and pain is just what Diarmuid needs. He’s a rubber band being stretched to his limit, and he can’t stand it. 

He breaks. A cry escapes his lips as he cums. Cú holds him steady, swallowing the load, then sits back with a smirk on his face.

He crawls forward and kisses Diarmuid again, letting him taste himself. “We’re not done yet.”

Diarmuid nods, too spent to give a verbal response. However, he yelps when Cú bites his shoulder.

“You can rest when I’m finished with you.” Cú laps at the blood flowing from the wound. “In the meantime, your Lord demands your attention.”

He doesn’t need to be told twice. Latching himself onto Cú, Diarmuid covers every inch he can reach with adoring caresses and kisses. He worships, whispering his idolatry into Cú’s chest, and his nerves tingle as he’s clutched closer. Pausing briefly, he traces the contours of the magnificent torso. In the dim light, Cú's definition is perfect, and Diarmuid can't help his twinge of awe. Who could ever compare to his lover?

Cú cups his face, tilting his head upward. He doesn't resist. Instead, he greedily melts into another kiss, his toes practically curling from desire. A chuckle from Cú reminds him of his task, and he quickly resumes his previous devotion. 

For several minutes, he strokes and sips and sighs until Cú growls, “Stop.”

His ministrations cease. He looks up, eager to please, and his heart skips a beat at the glazed expression on Cú’s face. Dilated pupils. Open mouth.

Oh yes, he’s done a good job.

Cú’s tail twitches. It snakes around and opens up a drawer next to the bed, procuring a bottle of lube.

“Get yourself ready,” comes the order.

Diarmuid is quick to obey. He carefully lathers the substance onto Cú’s cock, then prepares his own entrance. When he’s finished, Cú lifts him onto his lap—never breaking eye contact—then teases with one finger. Two. The tip of his cock prods, but doesn't enter.

Diarmuid is practically writhing now. "M-my Lord...  _please_."

Without warning, he's impaled. He cries out, face flushed, sweat clinging to his brow.

Like always, he trembles as he’s filled to the brim. It's a tight fit, and the sheer lust on Cú’s face is almost enough to make him cum yet again.

Slowly, Cú moves their bodies together. The tortuous pace leaves Diarmuid panting. He wants to beg again, _please, my Lord I need more_ , but he knows his pleas will fall on deaf ears. This is his punishment. The one Cú promised earlier.

Cú takes his sweet time. He rocks Diarmuid, gripping his hips, hitting the perfect spot with each thrust. Diarmuid implores with his eyes for a kiss. His request is granted, albeit briefly. The taste is over too soon, and Diarmuid can only gaze on in longing. _Please._

After an eternity, the pace starts to quicken, and Cú’s movements grow harsher. Diarmuid buries his face into Cú’s chest, moaning into his pecs. It’s starting to hurt, but it only adds to all of the other stimulation.

Grunting, Cú repositions him, laying him back on the bed. He thrusts feverishly, oblivious to any potential discomfort. It doesn’t matter, though. With one hand gripping his hair and another holding his leg up, Diarmuid is a slave to pleasure. He couldn't fight even if he wanted to. All he can do is scream his lover's name. 

He arches his back as Cú finally finishes. The Alter roars, grabbing his ass, spilling himself inside. The moment lasts a lifetime, yet it still ends too quickly.

They lay panting, entangled together for the foreseeable future. One last kiss seals the deal. They are both thoroughly drained. 

Cú rests his head, allowing Diarmuid to gently stroke his hair. He briefly admires the blue strands in the low light, and three words settle on his tongue. For a moment, they linger, but he swallows them. Now is not the time. This is his Lord. Though they share a bond, the phrase would not be reciprocated.

Even so, as tears brim his eyes, he mouths them while Cú cannot see.

_I love you._

**Author's Note:**

> Thanks for reading!


End file.
